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Subject: Ohms

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Original Message 1/9 03-Aug-04 @ 10:15 PM Edit: 03-Aug-04 | 10:25 PM - Ohms

0/d

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Hi,

Any of you buffs up to scratch on yer technical theory?

I need some help cause I want to connect my alesis M1's to an old technics hifi system (it has quite a good amp) but I'm worried about impedence problems. The speakers that came with it have an impedance of 8 - 16 ohms and the amplifier outputs an impedance of 8 - 16 ohms. I hate the sound of the speakers that came with it - far too bassy for my little room and I prefer the sound of my m1's - and they sound fine when i hook them up - but heres the problem - I'm worried cause they only have a rating of 4ohms - I don't know much about these things, only that imedance is the limiting of voltage or something - what does this mean in terms of damage or danger? Can anyone explain? Cheers,

S

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Message 2/9 04-Aug-04 @ 02:09 AM - RE: Ohms

Pongoid

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Here's sort of how it works: An Ohm is a measurement of resistance to electrical current. Now realize that the more current you put through an amplifier, the hotter it gets. Some amps are designed to handle more current, some are not. Now when you send a singal to an amp, it's going to try to push out as much current as you let it, in proportion to how much you put into it, and at what frequencies. The resistance gives the amplifier a load to push and pull against, only allowing so much current through, and leaving the rest unmoving. The lower the resistance, the more current moves, and the hotter the amps gets.

Imagine you're riding your bike and it's a fixed gear, meaning that you have to pedal to stay moving, no free-wheel and you're on flat ground. Now you come to a hill. That's resistance. If it's a hill going up, you have to use more energy to keep the same speed as on flat ground. Now if you're going downhill, you have to pedal fast to keep up with the wheels. In other words, the low resistance is sucking the power out of you. Well the same thing happens with amplifiers, and resistance. If your amp is only spec'd to 8 ohms and you put a 4 ohm load on it, you will burn it out if you turn it up, and will make it rather warm even at low volume. If you want to use 4 ohm speakers, get your self an amp that will handle the load. Good luck.

Ape

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Message 3/9 04-Aug-04 @ 05:23 AM - RE: Ohms

casparproject

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great explanation ape, you should be teaching this stuff

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Message 4/9 04-Aug-04 @ 05:33 AM - RE: Ohms

psylichon

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I think he is.

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Message 5/9 04-Aug-04 @ 06:08 AM - RE: Ohms

hakerman

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Yes, I don't recommend putting 4 ohm speakers with an amp that's only rated for 8. It will most likely overhead and not sound right.
Hifi systems are usually not good for powering monitors anyhow, you're probably better off getting a cheap second hand studio amp.

Thomas

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Message 6/9 04-Aug-04 @ 06:48 AM - RE: Ohms

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or he could use a resistor on the connecting wire to present more impedence to the amp

___________________________________

I had an idea for a script once. It's basically Jaws except when the guys in the boat are going after Jaws, they look around and there's an even bigger Jaws. The guys have to team up with Jaws to get Bigger Jaws.... I call it... Big Jaws!!!

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Message 7/9 04-Aug-04 @ 02:51 PM - RE: Ohms

craig

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If you do that you have to worry about how much power the resistor can handle, or you risk burning down your house

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Message 8/9 04-Aug-04 @ 05:10 PM - RE: Ohms

Pongoid

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Yeah, resistors generate heat, as the energy they are offering resistance to has to be shunted off in some way. Not the best solution. Better to have an amp with rails that will handle the throughput.

Ape

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Message 9/9 04-Aug-04 @ 06:31 PM Edit: 04-Aug-04 | 06:35 PM - RE: Ohms

0/d

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Overheat, bad for the amp, bad for the speakers - cool - so I might just go for a samson servo170 because i really wanna use the m1's - Anybody using a servo170 or bigger? Any good?

As for the theory, many thanks for the explanation pongoid but... I still don't get it -(pardon my ignorance - my grasp of physics is pretty much non existant.)

So, If my amp has 8ohms and my speakers has only 4ohms, surely it should be my speakers that overheat? Because more voltage is getting through the amp? Or is less ohms, more current? (In a manner of speaking) (ie. does less ohms equal less resistance and in turn equal more current getting through? )

Or wait, maybe I get it - is speaker voltage alternating? Does it go back to the amp and wreck it if it's not expended at the speaker?

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